Development and characterization of flexible thermally actuated electronic devices

One of the major challenges in the medical field is to develop electrodes that result both lightweight and comfortable for the users. Thin electronic devices have the capability to adhere to non-flat surfaces without changing their properties and performances, thus resulting in high levels of imperceptibility, high comfort level, and continuous use for the user. In parallel to the most studied conformable sensorized devices, soft electronics could be used to provide stimuli to the human body, for example through the development of tactile displays for visually impaired people, human-machine interfaces, or in real-life scenarios such as virtual reality. This PhD thesis highlights the possibility to use thermal actuation as a source for the development of “active” soft electrodes, capable of exerting force and displacements by the deformation of thin membranes. Inspired by this, examples of low-power wearable tactile displays based on the new approach were developed and tests conducted on a voluntary subject assessed the effectiveness of the implemented platforms. The generation of fast and highly localized temperature pulses using Joule heating also paves the way for the fabrication of thermal-based micro-devices both for sensing and actuation. As well as this, another strategy for the development of thermally activated devices is provided by thermoplasmonic nanoparticles. These materials absorb light - when irradiated at specific frequencies - which is re-emitted as heat. This behavior makes them nano-sources of heat, with the possibility of being finely tuned and suitably triggered remotely. In this PhD dissertation, two works related to thermoplasmonic show their applicability as invisible inks for advanced and flexible printable technologies and the implementation of smart materials capable of self-healing triggered by heat. All of the devices presented here were realized using rapid prototyping manufacturing techniques, demonstrating that bunches of such technologies can be fabricated within a day. This research pushes forward the prospect of implementing lightweight, flexible, and wearable active devices capable of eliciting tactile sensations on human skin, and also examines the possibilities offered by thermoplasmonic semiconductor nanoparticles within different fields of application.